The Whittle Turbojet

The propeller blueprint ends at a wall: as the blade tips approach the speed of sound, shock waves form, drag rises steeply and efficiency collapses. You cannot spin faster and you cannot lengthen the blade, because a longer blade has a faster tip at the same rpm. Frank Whittle saw this coming in 1929 as a young RAF officer and drew the way past it — stop trying to accelerate a large mass of air a little by pushing on it with blades, and instead accelerate a smaller mass of air a great deal by burning fuel in it. His patent lapsed in 1935 because the Air Ministry would not pay the renewal fee. The engine ran on a bench in 1937, shocking everyone present by accelerating out of control, and flew in the Gloster E.28/39 in 1941. This blueprint builds the thermodynamic cycle at bench scale and gates itself, because the honest version involves a spinning turbine and burning fuel.